Telephone system



Sept. 1, 1925.

1,551,748 L. o. KELLOGG TELEPHONE SYSTEM Filed Jan. 14 1921 m l @44 R W fiiirzzegz To all whom it may concern:

Patented Sept. 1, 192 5. i? 2 UNITED STATES 1,551,748 PATENT OFFICE- LEROY D. KELLOGG, OF DEERFIELD, ILLINOIS, ASSIGNO'R TO KELLOGG'SWITGHBOARI) 1 AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

' TELEPHONE SYSTEM.

Application filed January 14, 1921. Serial No. 437,169.

Be it known that I, LEROY D. KELLOGG, a citizen of the United States of America, residing at Deerfield, county of Lake, and State of Illinois, having invented certain new and useful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to telephone systems andhas to do moreparticularly with automatic or semi-automatic systems in which switches are used for connecting a calling line to an idle trunk, and an object of my invention is the provision of an improved arrangement which embodies desirable features and advantages, all in an eflicient, siinple,,economical manner, and in which the switch of my invention is most positive in its operation. V a

Line switches or individual switches as now most generally used are provided with off-normal contacts which assume their alter nate positions during a period of the operation of the switch to bring about circuit changes of the switch for the proper functioning of the same, and a feature of my invention is the provision of an individual switch in which no off-normal contacts are used and in which the circuit changes for the functioning of the switch are brought about entirely by simple relays, excluding all interlocking mechanism between relays or relays that close certain contacts on a partial energization and others on more complete energization.

Another feature of my invention is the provision of a switch of the non-restoring type, that is, one which remains in contact with terminals of the trunk last used when disconnection is effected, and which will 1 again seize the trunk last used when a call is initiated, provide-d the trunk in the meantime has not been seized by another switch and is in use at the time the call is made.

Another feature of myinvention is the provision of a switch with a positive drive circuit that does not permit the wipers of the switch to stop on busy contacts nor to pass over idle contacts. The non-restoring switch may be of the general type illustrated are attained will be; described by reference to the accompanying drawing, in which I illustrate diagrammatically an automatic telephone system including the line switch of my invention. I l Referring now more in detail to my inventlon as illustrated in the accompanying drawing,to the left thereof I illustrate a calling substation A which includes the usual talking equipment, with the addition of a calling device CD. The calling substation A connects at the exchange with the line switch B of my invention, comprising a rotary shaft which carries the test or private wiper 2 and a pair of line wipers 3 and 4t; A line relay LR is provided which is energized over the subscribers line conductors,

and a cutoff relay CO is also provided which is energized when an idle trunk is seized to extend the connection from the calling substation to the seized trunk. The motor magnet MM, through the agency of a ratchet and pawl mechanism steps the shaft in a rotary direction to advance the wipers 2, 3 and-4= over contacts 5, 6 and 7 upon the back stroke of the pawl of the motor magnet MM, as is well understood. 7

The connector C comprises an impulse relay IR, which relay IR is energized over the line when an idle connector as C is seized and is de-energized and energized by impulses from the calling substation A to bring about the primary movement of the wipers 8, 9 and lO through the agency of the primary magnet PM. A switching relay SW is provided which, when energized, connects the secondary magnet SM to be acted upon by impulses to stepthe wipers 8, 9 and 10 in a secondary direction I over contacts 11, 12 and 13 to engage the contacts of the called line. A test relayTR is provided which tests the called line as to its idle or busy condition, and when busy connects a suitable busy tone from the busy back apparatus BB to. notify the calling subscriber of the busy condition of the called line. A ringing control relay RC is provided which connects the ringing generator RG and interrupter I in circuit to intermittently apply ringing current to the called] line, when the said line is idle. A relay SR is also provided which is energized when the subscriber at the called substation answers. Primary off-normal contacts PON are provided which assume their alternate position upon the first step of the wipers 8, 9 and 10 in a primary direction, and secondary offnormal contacts SON are also provided which assume their alternate position upon the first step' of the wipers 8, 9' and 10 in a secondary direction.

To the right of the drawing I illustrate 2. called substation D similar to the calling substation A and connecting at the exchange with a line circuit B similar to that of B.

Having described in general the apparatus as illustrated in the accompanylng drawing, I will now describe in detail the operation of the system including the individual line switch of my invention.

Assuming now that a call is to be traced from the calling substation A to the called substation D, upon the removal of the receiver by the subscriber at the calling' substation A, line relay LR of the individual line" switch B energized over a circuit traced from battery through the winding of line relay LR, conductor 14, normal contact of motor magnet MM, conductor: 16, normal contact 17 of cut-01f relay CO, through the substation A, back through normal contact 18 of cut-offrelay CO, conductor 19 to ground at normal contact 20 of the motor magnet MM. Wipers 2, 3 and 1' always rest upon the set ofcontacts 5, 6 and 7 last used, and assuming that the contacts upon which the wipers now rest are busy due to another subscribers line circuit having selected the connector last used by the subscriber A, the private contact 5 will be grounded. Energized line relay LR closes its contacts 21 and 22, establishing an energizing circuit for the relay 23, traced from battery through the winding of relay 23, conducto'r'2 l, normal contact 25 of motor magnet MM, conductors26 and 27, alternate contact 22 of line relay LR, conductor 28, normal contact 29 of cut-0E relay CO, conductor 30 and wiper 2 to the engaged rounded busy contact 5. The cut-ofi' relay 0 is shunted when the wiper 2' is engaging a busy grounded contact 5, the said shunt being traced from ground at the busy" contact 5, wiper 2, conductor 30, normal contact 29 of cut-oft relay CO, conductor 28, alternate contact 21 of line relay LR, conductor 31, normal contact 32 of cut-01f relay CO, through the winding of cut-01f relay COto ground at normal contact 33 of relay CO. A circuit also extends through relays 23, and CO from battery through the winding of relay 23, over conductor 24, normal contact 25, conductors 26 and 27, alternate contacts 22 and 21, conductor 31, normal contact 32' of relay CO, through the winding of relay CO to ground at normal contact 33 of relay CO. This circuit just traced has no energizing effect on the cut-off relay CO at this time due to the shunt about said relay CO as above traced, but when an idle contact 5 is engaged by the wiper 2, the relay CO will energize over the above traced circuit, as will be more fully hereinafter described, because the engaged contact 5 will not be grounded.

The relay 23 upon energization closes itsalternate contact 34, establishing an energizing circuit for the motor magnet MM, traced from battery through the winding of the motor magnet RIM, conductors 35 and 36, to ground at alternate contact 34; of relay 23. The motor magnet MM, upon energization, opens its normal contact 25, thus opening the energizing circuit of the relay 23, and the relay 23 upon de-energization opens its alternate contact 34 to open the energizing circuit of the motor magnet MM, and the motor magnet MM upon de-energization steps the wipers 2, 3 and l into engagement with the next set of contacts 5, 6 and 7. Should the contacts now engaged by the wipers be busy, relay 23 will again be energized over the previously described path, and the said relay 23 in turn will again close a circuit through the motor magnet MM, as before described. The relay 23 and motor magnet MM are thus alternately energized and (lo-energized, the motor magnet 11M stepping the wipers 2, 3 and l from one set of contacts 5, 6 and 7 to the next, as long as busy, i. e., grounded, contacts are cncountered. Magnet MM alternately opens and closes contact 25, and thus a vibratory circuit is closed through the winding of relay CO, as before described, but due to' the shunt about relay CO, as before described, the cutoff relay CO at this time remains inert. The ground at alternate contact 34; of relay 23 extending over conductors 36 and 35 through normal contact 37 of relay CO to the calling lines private normal contacts 38 at the connectors having access to it to render such contacts busy against selection. This ground will be of a vibratory character, and I accordingly so construct the test relay TR of the connector to be somewhat slow to release its armatures. Consequently, the calling line will test busy while its line switch travels, as will be understood from the general operation of the connector C. The motor magnet MM alternately opens and closes its normal contacts 15 and 20 during the selecting operation of the switch 13, interrupting the energizing circuit of the line relay LR, but due to the slow-to-release construction of the line relay LR it is not afiected by the rapid interruptions of motor magnet MM.

When an idle private contact 5 is encountered by the wiper 2, the relay 23 and motor magnet MM remain unoperated, because the private contact 5 now engaged is free from ground and the shunt about cut-off relay CO is removed and the circuit from battery through the windings o f relays 23 and CO to ground at normal contact 33 of relay GO, as before described, allows the cut-off relay CO to energize, but the relay 23 does not energize over this circuit on account of the resistance of relay CO and remains inert. The relay CO upon energization opens its normal contacts 29 and 33 and. thus opens its initial energizing circuit, but the said relay CO being slow to release is held up momentarily until a substitute circuitis established for it, as will presently be described. The relay CO also upon energization shifts its contacts 17 and 18, opening the energizing circuit of the line relay LR, which now restores to normal, and the relay CO, also closes its alternate contact 37, connecting ground to the contacts 38, keeping them busy until the termination of the conversation.

Should the substation A be sized as a. called line by a. connector engaging contacts 38, 12 and 13, ground will be extended to the private contact 38 from the connector, as will be more fully hereinafter described, and this ground extends from the contact 38 through normal contact 37 of relay CO, conductor 35, to battery through the winding of motor magnet MM. The motor magnet MM energizes and opens its normal contacts and so that when the subscriber at the substation 'A removes his receiver from. the switch-hook as a called line, no energizing circuit for the line relay LR is established and the motor magnet MM, upon energization, thus removes the substation control the line switch B when the line is a called line. Upon release the motor magnet MM deenergizes and as the motor magnet MM advances the wipersupon its back stroke they are stepped into engagement with the next set of contacts.

The relay CO having energized, its contracts 17 and 18 assume their alternate positions, the wipers 2, 3 and 40f the individual switch B are now connected to the contacts 5, 6 and 7 of the idle connector G, thus extending the calling line to the seized idle connector C. A circuit is established for the impulse relay IR of the connector C. traced frombattery through left-hand winding of relay IR,'contact 6, wiper 3, alternate-contact 17 of relay CO, through substation A, back through alternate contact 18 of relay CO, wiper 4, contact 7,

to ground through the righthand winding of relay IR. The closing of alternate contact 40 of the impulserelay IR establishes 1 and 48, alternate contact 49 of relay IR to ground at alternate contact 40 of relay IR. The relay 41 upon energization closes a locking circuit for itself, traced from battery through the right-hand winding of relay 41 to ground at its alternate contact 50 of relay 41. The closing of alternate contact 40 of relay IR establishes a subof relay CO, its alternate contact 33, con

ductoir 30, wiper 2, contact 5, conductors 45 and 46 to ground at alternate contact 40 of the impulse relay IR. Relay 23 does not operate over this circuit for reasons as before described. I

If the private contact 5 engaged by the wiper 2 is idle when the subscriber initiates a call, the line relay LR is energized, as

before described, and operates to close its alternate contacts 21 and 22. 'Ilherebeing no ground on the private contact 5, no shunt will be closed about the relay CO, as before described, and relay 23 will not energize, and in remaining inert its alternate contact 34 remains open and therefore no energizing circuit is established and motor magnet MM does not energize and the I wipers 2, 3 and 4,'therefore, remain in engagement with the contacts 5, 6 and 7, that were last used by the switch B in establish ing a connection. The cut-off relay CO, is, therefore, immediately energized from battery through relay 23 and winding of relay CO to. ground at normal contact 33,

as before described, and the ope-ration of the circuit from this point on is the same as above described. Thus, the switch only engagement with a. busy trunk when a call is lnltlated.

The energizatlon of relay IR havmg brought about the energization of relays 41 and 42, as already described, assuming that the called subscribers number at substation D is 45, the subscriber A now operimpulses bring about four de-energizations and energizations of the relay IR, causing the primary magnet PM to energize and de-energize four times to step the wipers 8,9 and 10 in a primary direction to the fourth group of contacts, that group containing the cont-acts of the called line. The circuit of the primary magnet PM may be traced from battery through the winding of the said magnet, normal contact 51 of switching relay SW, conductor 52, alternate contact 53 of relay 42, normal contact 49 of retravels when its wipers 2, 3 and 4 are in j lay'IR, conductor 46, conductor 45, and nordue. to its differential action, to neutralize and restore its contacts to normal. Relay 42 does not restore during the sending of impulses due to its adjustment, construction, and the rapidity of the interruptions of con* tact 49.1 It will be noted that the relay when first .energized had its upper winding immediately energized by contact 50 of relay 41, and was ina neutral condition with its armatures retracted when relay IR sent the first impulse, but immediately energized when relay IR opened the circuit through the-lower winding of relay 42. The closing of normal contact 56 of relay 42 brings about the energization of the switching relay. SW, by current traced from battery through the winding of said relay SW, its make-beforebreak contact 57, normal co-ntact 58 of secondary off-normal springs SON, conductor 59, normal contact 56 of relay 42, and conductor 60 to ground at alternate contact 61 of primary oifinormal contacts PON, the said primary off-normal contacts PON having been moved to their alternate position on the first step of the Wipers 8, 9'and 10 of the connector switch. The closing of alternate contact 51 of the switching relay SIV now renders the secondary magnet SM operative so that when the calling subscriber at the substation A actuates his call device to send the last set of impulses, which we have assumed are live in number, the said magnet SM will be energized and deenergized by the impulse relay IR five timesover a circuit traced from battery through the winding of the said magnet SM, alternate contact 51 of re lay SVV,.conductor 52, alternate contact 53 of relay 42, normal contact 49 of relay IR, conductor 46, conductor 45, and alternate contact 44 of the primary oft-normal contacts PON and conductor 62 to ground at normal contact 54 of relay 55. The secondary magnet SM now steps the wipers 8, 9 and 10 in a secondary direction to engage contacts 11, 12 and 13 of the called line. Upon the first impulse of the last set, the relay 42 again energizes to permit the secondary. magnet SM to be operated, and after'the last impulse the relay 42 is again tie-energized, as previously described. restoration of. the relay 42 closes acircuit for the test relay TR, traced from battery T hethrough the winding'of the said relay, conductor 63,.the alternate contact 64 of relay SIV, alternate contact 58 of the secondary oil-normal contacts SON, (saidv contacts. having been moved to their alternate position upon the first step ofthe wipers in their secondary direction), conductor 59, normal contact 56 of relay 42, conductor 60 to ground at alternate contact 61 of. the primary off-normal contacts PON. The closing of alternate contact 65 of relay TR connects the said relay over conductor 66 to the test wiper 8, and should the called line be busy the private contact 11 of the called line would be grounded, thus closing a locking circuit for the said relay TR. through the private wiper.

UaZZecZ' Zine idle.

Assuming that the called line. is idle, private contact 11 of. the called line will have a battery potential. upon it, and the relay TR will not remain energized but will de-energize. The opening of normal contact 67 of relay TR opened the circuit ofthe switching relay SW. The relay SIV, (lo-energizing, opens the circuit for-relay TR at its contact 64, leaving the relay TR dependent upon the potential. foundupon the private contact 11 of the calledline for its holding potential, and, as assumed, this contact is free from ground potential; therefore, the relay TR de-energizes and returns to normal. The relay TR de-energizing causes the energization of the relay 55 over a circuit which maybe-traced from battery through the motor magnet. MM of the line switch B of the called line, conductor 36, normal contact 87 of relay CO, to bank contact 11, through wiper 8, conductor 66, normal contact 65 of relay TR, conductor 70, normal contact 71 of relay SIV, conductor 72, through-the lower winding of the relay 55, and conductor 73 to ground at alternate contact 74' of relay 41. The closing of alternate contact 75 of relay 55 short-circuits the lower winding, of the. said relay, and the closing of alternate contact 76 of relay 55 closes a circuit through the upper winding of the said relay, through the alternate contact 76 and conductor 73 to ground at alternate contact 74 of relay 41. The motor magnet Mh of the line switch B associated with the called line. is energized over this circuit and remains energized until conversation has terminated.

The closing of alternate contact 77 of relay 55 connects the interrupter I to the relay 78. The circuit for relay 78 may be traced from battery through the winding of the said relay 78, conductor 79, alternate contact 77 of relay 55, conductor 80, normal contact 81 of relay RC and, through. the interrupter I to ground. The relay 78 is thus intermittently energized and de-energized by the rotating interrupter I, and upon each de-energization of the relay 78 the ringing generator RG is connected to the called line over a circuit extending from the ungrounded pole of the generator RG, through normal contact 82 of ringing control relay RC, conductor83, alternate contact 84 of relay 55 conductor 85, normal contact 86 of relay 78, wiper 10, bank contact 13, through the condenser and call bell of the called substation D, back through bank contact 12, wiper 9, normal contact 87, of relay 78, and conductor 88 to ground at alternate contact 54 of relay 55.

The call bell of the called subscriber at the substation D is thus intermittently rung, due to the energization and de-energization of the relay 78 by the interrupter I. When the called subscriber answers and the relay 78 is in its energized position, a circuit for therelay SR is closed, which may be traced from battery through the lower winding of the relay SR, through alternatecontact 86 of relay 78, wiper 10, contact 13, through the now closed contacts of the'substation switch-hook at the called substation D, back through contact 12, wiper 9, alternate contact 87 of relay 78, and

through the upper winding of the relay SR to ground. The relay SR, upon energizing, closes an energizing circuit for the ringing control relay RC, which may be traced from battery through the winding of the said I relay RC, its make-before-break contact 89 to ground at alternate contact 90 of relay SR. The closing of alternate contact 9170f relay RC closes a locking circuit for the said relay which may be traced from battery through thewinding of said relay, its alternate contact 91 and conductor 60 to ground at alternate contact 61 of the primary ofl-normal contacts PON. The opening of normal contacts 81 and 82, upon the energization of relay vRC, disconnects the interrupter I and the ringing generator RG to prevent further application of ringing current. -A substitute circuit for the relay 78 is now established which may be traced from battery through the winding of the relay 78, conductor 79, alternate contact 77 of relay 55, conductor 80, alternate contact 81, of relay RC, and conductor 60 to ground at alternate contact 61 to primary ofii-normal contacts PON. The subscribers are now in conversational circuit, and the talking circuit may be traced over the heavily marked conductors, said conductors having the condensers K and K interposed.

The subscribers having finished conversation, and assuming that the subscriber at the called substation A is first to replace his receiverupon the switchhook, the opening of the switch hookco-ntacts brings about the de-energization of the impulse relay IR of the connector G. W The restoration of the relay IR brings about the opening of the holding circuit of the relay CO of the individual switch B, which relay CO restores and places the individual switch B, in condition to be used in establishing another connection.

The subscriber D restoring his receiver upon its switchhook interrupts the circuit of the relay SR at the switchhook contacts,

causing the said relay to dc-energize. The

closing of normal contact 95 of relay SR closes a circuit through the left-hand winding of the relay 41, which may be traced from battery through the left-hand winding of the said relay 41, alternate contact 96 of relay 41, conductor 97, normal contact 95 of relay SR and conductor 98 to ground at normal contact 40 of relay IR. Due to the difierential construction of relay 41, the said relay neutralizes and restores to normal. The closing of normal contact 99 of relay 41 closes an energizing circuit for the secondary magnet SM, which may be traced from battery through the winding of said secondary magnet SM, conductor 100, normal contact 99 of relay 41, alternate contact 1010f the primary off-normal contacts PON, through the interrupter I to ground. The secondary magnet SM thus steps the wipers 8, 9 and 10 beyond the last set of contacts in the group and the wipers then restore to normal from this position by spring tension. The restoration of the relay 41 brings about the opening of the circuit of the relay 55 atalternate contact 74, and the relay 55 restoring'opens the circuit of relay 78 at contact 77 of relay 55, and the primary off-normal contacts PON having restored, upon the restoration of the switch, the opening of the alternate contact 61 of PON brings about the de-energization of the relay RC. The relay 41 also brings about the de-energization of the motor magnet MM of the line switch B which is associated with the called subscriber D, and magnet MM upon releasesteps the wipers of the switch B into engagement with the next set of contacts of the switch B, and they rest there whether or not the contacts are busy. All three wipers of switch B are at this time on open circuit. All the apparatus used in establishing a connection between a calling subscriber at the substation A and the called subscriber at the substation D is now atnormal and available for use in establishing other connections.

Assuming now that the subscriber at the called substation D was first to replace his receiver upon the switchhook, the opening of the switchhook contacts at the substation D brings about the de-energization of the relay SR. Nothing else happens at this time as the relay IR is still maintained energized over the line oi the calling substation The calling subscriber at the substation A replacing his receiver -inter rupts the circuit of the impulse relay IR at the switchhook contacts. The relay IR deenergizing closes a circuit for the lefthand winding of relay s1, causing the said relay to de-energize, as hereinbet'ore described. The restoration of the individual switch B and connector 0 is the same as previously described from this point on. Should the called subscriber D fail to replace his receiver upon the switchhook after the conversation is terminated, the replacing of the receiver at the substation A brings about the de-energization of the impulse-relay IR of connector .0, the same as before, and the opening of alternate contact .40 of impulse relay IR opens the circuit of the relay C0 of individual switch B as before described, and causes the release of switch B.

The subscriber at the called substation failing to replace his receiver, permits the continued energization of the relay SR, this holding the contact 95 of said relay in its alternate position, preventing the differ vential wound relay 41 from restoring to normal and closing. the energizing circuit for the secondary magnet SM. The relay 12 energizes when the line relay IR drops back but is immediately restored to normal due to the closure of an energizing circuit through the lower winding of the said relay 42, which may be traced from battery through the said lower winding, conductor 47, alternate contact 95, connector 98, to ground at normal contact 40 of the now restored impulse relay IR. Relay &2 being diiterentially wound,-restores to normal, and

the closing of normal contact 102 of the said relay: 12 places a ground upon the private contact of the connector Cover a circuit which may be traced from ground at alternate contact 61 of the primary citnormal contact PON, conductor 60, normal contact 56 ofrelay 42, conductor 59, alternate contact 58, normal contact 102, alternate contact 103 of the secondary off-normal contacts SON. to the private contact 5. The placing of this busy potential upon the private contact prevents any individual switch B from engaging the contacts of this busy connector.

Called Zine busy.

Assuming now that the called line is busy, the operation of the circuit is the same BB torthe line to transmit a busy signal to said calling subscriber at substation A, thus notifying him of the busy condition of the said called substation D. The relay TR upon locking up to ground at the private contact 11, closes a circuit for relay RC, traced from battery through the winding of relay RC, make-beforebrea-k contact 89, normal contact 90 of relay SR, normal contact 6 1 of relay SIV, conductor 63, alternate contact 65 of relay TR, and conductor 66 to the grounded private contact 11. The relay RC thus closes a locking circuit for itself, traced through the winding of said relay RC, alternate contact 91, conductor 60 to ground at alternate contact 61 of the off-normal contactsPON. Now, should the line called becomeidle during the time the busy signal is being transmitted to the calling substation,the falling back of relay TR will not cause the called subscriberto be signaled owing to the fact that relay RC is locked up to ground at contact 61. The calling subscriber now replaces his receiver, bringing about the de-energization of the impulse relay IR. The relay IR restoring, opens the circuit of the relay C0 of the individual switch B to place the switch in condition for establishing other connections as previously described. The relay IR de-energizing brings about the restoration of the relay 11, due to the fact that the relay SR has not been energized. The closing of the circuit: through the lefthand winding of thecircuit 41 brings about the neutralization of .the said relay ll. The closing of normal contact 99 of the said relay 41 closes acircuit through the secondary magnet SM, which magnet steps the wipers 8, 9 and 10"beyond the last set i of contacts. The wipers then restore to normal by spring tension. The primary oft-normal contacts FUN and secondary oft normal contacts SON are also restored, and the-apparatus used in this busy connection is now at normal and available for use in establishing other connections.

lVhile I have shown av system of 100 serting first selectors, the system may be increased to a 1000 system, etc.

It is to -be understood that I do not wish to'be limitedto the exact matters as shown,

as various other arrangements may readily suggest themselves to one skilled in the art. Therefore, I desire to cover all such changes and modificationsas come within the spirit and scope of the appended claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. A'telephone line having anauto-matic non-restoring selecting switch including a line relay and a travel controlling magnet energized responsive to said relay, means 'lOO ill)

controlled by said magnetto disconnect said relay from the line when connected to as a called line, and another relay for controlling contacts in the circuits of said line relay and said magnet.

2. A telephone line having an automatic non-restoring switch and a line relay 'to render the stepping magnet of said switch active to select an idle trunk line, contacts of said magnet in the circuit of said relay, connections to actuate said magnet when the line is called to disconnect said relay, and another relay -I'o-r controlling contacts in the circuits of said line relay and said magnet.

3. A telephone line having an automatic selecting switch, a relay energized by current over said line to set up travel of said switch in search of an idle trunk, private contacts engaged by said switch and a pair of electromagnets their windings connected together and in series with a source of current, one terminal of said source connected to busy contacts only and between said windings when said switch engages such contacts to short circuit one of said windings, the short-circuited magnet energizing when the short circuit ends, talking contacts controlled by csaid magnet, and a motor magnet for eflecting the travel of said switch, said motor magnet controlled by said electromagnets.

4. A telephone line having an automatic selecting non-restoring switch, and a line relay for energization to initiate travel thereof, a driving magnet for effecting travel of said switch, private contacts successively engaged by said switch in its travel, a. relay for said switch in series with battery during travel but short-circuited by a terminal of said battery connected to busy contacts engaged by said switch, the engagement of an idle contact ending such short circuit and actuating said relay, means controlled by said relay on energization to connect its winding to the idle contact and lock itself thereover and talking circuit contacts controlled by said relay, another relay for said switch, said driving magnet controlling a contact in the circuit of said last relay, and said last relay controlling a contact in the driving circuit of said driving magnet, said last relay and said driv ing magnet energizing and de-energizing alternately in eilecting travel of said switch.

5. A telephone line having a selecting switchand a line relay, a travel controlling magnet for the switch having contacts actuated to disconnect the line relay when connection is made to said line as a called line, and another relay having contacts to disconnect said line relay when the line is a calling line, said magnet adapted to drive said switch in its progressive direction.

6. In an automatic telephone system a line having an automatic switch, a motor magnet for operating said switch when a call is extended from said line and, also operable to prevent the operation of said switch when said line is connected to as a called line, and means for releasing said switch at the end of conversation by causing it to step into engagement with the adjacent contact set. a

7. A telephone line having an automatic switch, and a relay energized when the line is a calling line and its switch is engaging idle contacts, switching contacts of said relay actuated on energizat-ion to break the normal connections of both its windings terminals, and a locking circuit controlled by said relay.

8. In an automatic line switch for telephone systems or the like, a stepping magnet, a telephone line, means controlled by said magnet for intermittently applying a busy' potential to terminals of said line, a test terminal adapted to be applied to said first terminals, and a sluggish test relay connected to said test terminal.

9. In a line switch for telephone lines, contact. wipers for said switch, a stepping magnet for moving said wipers, said magnet.

being in a circuit organization such that its armature contacts cut oil the line wires when the line is called without effecting the movement of said wipers.

10. In a non-restoring line switch for telephone lines having a stepping magnet, a line out on relay, a line relay having its normal circuit through a back contact of said stepping magnet, and through a back contact of said line out on relay.

11. In a non-restoring line switch for telephone lines, a line relay and a step-ping magnet having their circuits connected through contacts ofa line out on relay, and means including a relay in circuit in series with said line cut on relay for short-circuiting said last relay while the switch is traveling and also for controlling the operating circuit of said stepping magnet.

1.2. A line switch for telephone lines having a stepping magnet serving also as a line out off relay when the line is called. cont-act wipers for said switch adapted to be operated by said magnet but not. affected by said magnet when the line is called, a line cut-on. relay for extending said line toward the calling line, means including circuit connections to short-circuit said last relay while the switch travels and to energize it when the switch stops, and a line relay for controlling the initial travel of said switch when the line is calling, said stepping magnet controlling the initial energizing of said line relay.

13. A non-restoring switch for automatic telephone systems having a line relay to .relay short-circuited during travel of the switch, its short circuit including a contact of the line relay and a contact of said driving magnet, said driving magnet also controlling contacts in the circuit of said line relay, and means for energizing said second relay when the switch stops.

14. An automatic non-restoring line switch for an automatic telephone system including a line relay, a circuit for said line relay, an electromagnet that cuts said line relay off intermittently during the operation of said switch in extending a call, a line out on relay that cuts said relay 01? continuously when the call is extended beyond said switch, said electromagnet rendering both said line relay and said line out on relay inoperable when the line associated with said switch is connected to as acalled line.

Signed by me at Chicago, in the county of Cook and State of Illinois, this 12th day of January, 1921.

LEROY D. KELLOGG. 

